The present disclosure relates to a process to upgrade light paraffins, preferably C2-C5, to paraffinic hydrocarbon fluids. The process is particularly applicable to the upgrading of iso-paraffins, which are abundantly found in Natural Gas Liquids (NGL) and tight oils (produced from shale or sandstone), as well as fractions from various refining and/or chemical streams.
With the increasing production of shale gas and tight oils, the supply of light paraffins (e.g., C2-C8, especially C2-C5 paraffins) is increasing at an unprecedented rate in the North America region; a large fraction (up to 30%) of NGL, for example, is C4/C5 paraffins. At the same time, demand for C4/C5 molecules is decreasing due to a number of factors: (1) steam crackers switching feed from light naphtha to ethane; (2) shrinkage of the gasoline pool in the North American market; and (3) a potential mandate for gasoline Reid Vapor Pressure (RVP) reduction. Although diluent use of C5s for heavy crude is predicted to grow somewhat, the supply of C4s/C5s is quickly outpacing demand and the imbalance will become worse with time.
Profitable dispositions for ethane (e.g., cracking to make ethylene and propane (e.g., dehydrogenation to make propylene) exist, Upgrading C4/C5 paraffins to higher value and large volume products, while desirable, remains challenging. Conversion of C4/C5 paraffins to heavier hydrocarbon products such as gasoline, kerojet, diesel fuels, and lubricant basestocks would provide a large volume and higher value outlet to help alleviate the excess of light ends in the North American market, But there is no current commercial process directly converting light paraffins to heavier hydrocarbons such as these. Conventional upgrading practices first convert light paraffins to olefins via cracking or dehydrogenation, followed by olefin chemistries such as oligomerization or polymerization, alkylation, etc., to build higher molecular weight molecules. A number of technologies are known to convert light paraffins to aromatics such as BTX (benzene, toluene, and xylenes), including the Cyclar™ process developed by UOP and the M2-Forming process developed by Mobil Oil Corporation.
Hydrocarbon fluids (also known as hydrocarbon solvents), such as ExxonMobil's Isopar™, are high-purity synthetic iso-paraffins. Hydrocarbon fluids are widely used in paints, personal care products, industrial cleaning, machining and metal works, printer ink toners, polishing and waxing, crop protection, as well as in air fresheners. The products need to be odorless, stable, having narrow boiling ranges (for optimal combination of flash point and drying time), low aromatic content (to minimize risks from exposure), low freeze point, and compatible with most packaging materials.
Currently, paraffinic hydrocarbon fluids are experiencing increased demand. Paraffinic hydrocarbon fluids are traditionally produced via two main routes, both requiring iso-butene: (1) alkylation of iso-butene with iso-butane over an acid catalyst; and (2) oligomerization of C4 olefins such as iso-butene, followed by hydrogenation to saturate the double bond. As iso-butene is typically in limited supply, there still remains a need for a process for producing paraffinic hydrocarbon fluids using readily available feedstocks, such as light paraffins.